Demonstrators battle with police during a march to support striking public high school teachers Oct. 7 in Rio de Janeiro. A small number of demonstrators fired incendiary devices at police who used tear gas to disperse the crowd. Antonia Lacerda, epa

A protester is assisted after being overcome by tear gas in Rio de Janeiro. Mario Tama, Getty Images

A demonstrator jumps over a burning barricade at Cinelandia Square. Felipe Dana, AP

A masked protester marches with a makeshift shield. Felipe Dana, AP

Protesters stand during a demonstration by teachers and supporters. A small group fired incendiary devices at police who responded with tear gas. Mario Tama, Getty Images

Police capture a demonstrator. Antonia Lacerda, epa

Demonstrators take cover from tear gas fired by riot police outside the City Council building. Felipe Dana, AP